1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef __ASM_ALTERNATIVE_MACROS_H 3 #define __ASM_ALTERNATIVE_MACROS_H 4 5 #include <asm/cpucaps.h> 6 7 #define ARM64_CB_PATCH ARM64_NCAPS 8 9 /* A64 instructions are always 32 bits. */ 10 #define AARCH64_INSN_SIZE 4 11 12 #ifndef __ASSEMBLY__ 13 14 #include <linux/stringify.h> 15 16 #define ALTINSTR_ENTRY(feature) \ 17 " .word 661b - .\n" /* label */ \ 18 " .word 663f - .\n" /* new instruction */ \ 19 " .hword " __stringify(feature) "\n" /* feature bit */ \ 20 " .byte 662b-661b\n" /* source len */ \ 21 " .byte 664f-663f\n" /* replacement len */ 22 23 #define ALTINSTR_ENTRY_CB(feature, cb) \ 24 " .word 661b - .\n" /* label */ \ 25 " .word " __stringify(cb) "- .\n" /* callback */ \ 26 " .hword " __stringify(feature) "\n" /* feature bit */ \ 27 " .byte 662b-661b\n" /* source len */ \ 28 " .byte 664f-663f\n" /* replacement len */ 29 30 /* 31 * alternative assembly primitive: 32 * 33 * If any of these .org directive fail, it means that insn1 and insn2 34 * don't have the same length. This used to be written as 35 * 36 * .if ((664b-663b) != (662b-661b)) 37 * .error "Alternatives instruction length mismatch" 38 * .endif 39 * 40 * but most assemblers die if insn1 or insn2 have a .inst. This should 41 * be fixed in a binutils release posterior to 2.25.51.0.2 (anything 42 * containing commit 4e4d08cf7399b606 or c1baaddf8861). 43 * 44 * Alternatives with callbacks do not generate replacement instructions. 45 */ 46 #define __ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg_enabled) \ 47 ".if "__stringify(cfg_enabled)" == 1\n" \ 48 "661:\n\t" \ 49 oldinstr "\n" \ 50 "662:\n" \ 51 ".pushsection .altinstructions,\"a\"\n" \ 52 ALTINSTR_ENTRY(feature) \ 53 ".popsection\n" \ 54 ".subsection 1\n" \ 55 "663:\n\t" \ 56 newinstr "\n" \ 57 "664:\n\t" \ 58 ".org . - (664b-663b) + (662b-661b)\n\t" \ 59 ".org . - (662b-661b) + (664b-663b)\n\t" \ 60 ".previous\n" \ 61 ".endif\n" 62 63 #define __ALTERNATIVE_CFG_CB(oldinstr, feature, cfg_enabled, cb) \ 64 ".if "__stringify(cfg_enabled)" == 1\n" \ 65 "661:\n\t" \ 66 oldinstr "\n" \ 67 "662:\n" \ 68 ".pushsection .altinstructions,\"a\"\n" \ 69 ALTINSTR_ENTRY_CB(feature, cb) \ 70 ".popsection\n" \ 71 "663:\n\t" \ 72 "664:\n\t" \ 73 ".endif\n" 74 75 #define _ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg, ...) \ 76 __ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg)) 77 78 #define ALTERNATIVE_CB(oldinstr, cb) \ 79 __ALTERNATIVE_CFG_CB(oldinstr, ARM64_CB_PATCH, 1, cb) 80 #else 81 82 #include <asm/assembler.h> 83 84 .macro altinstruction_entry orig_offset alt_offset feature orig_len alt_len 85 .word \orig_offset - . 86 .word \alt_offset - . 87 .hword \feature 88 .byte \orig_len 89 .byte \alt_len 90 .endm 91 92 .macro alternative_insn insn1, insn2, cap, enable = 1 93 .if \enable 94 661: \insn1 95 662: .pushsection .altinstructions, "a" 96 altinstruction_entry 661b, 663f, \cap, 662b-661b, 664f-663f 97 .popsection 98 .subsection 1 99 663: \insn2 100 664: .previous 101 .org . - (664b-663b) + (662b-661b) 102 .org . - (662b-661b) + (664b-663b) 103 .endif 104 .endm 105 106 /* 107 * Alternative sequences 108 * 109 * The code for the case where the capability is not present will be 110 * assembled and linked as normal. There are no restrictions on this 111 * code. 112 * 113 * The code for the case where the capability is present will be 114 * assembled into a special section to be used for dynamic patching. 115 * Code for that case must: 116 * 117 * 1. Be exactly the same length (in bytes) as the default code 118 * sequence. 119 * 120 * 2. Not contain a branch target that is used outside of the 121 * alternative sequence it is defined in (branches into an 122 * alternative sequence are not fixed up). 123 */ 124 125 /* 126 * Begin an alternative code sequence. 127 */ 128 .macro alternative_if_not cap 129 .set .Lasm_alt_mode, 0 130 .pushsection .altinstructions, "a" 131 altinstruction_entry 661f, 663f, \cap, 662f-661f, 664f-663f 132 .popsection 133 661: 134 .endm 135 136 .macro alternative_if cap 137 .set .Lasm_alt_mode, 1 138 .pushsection .altinstructions, "a" 139 altinstruction_entry 663f, 661f, \cap, 664f-663f, 662f-661f 140 .popsection 141 .subsection 1 142 .align 2 /* So GAS knows label 661 is suitably aligned */ 143 661: 144 .endm 145 146 .macro alternative_cb cb 147 .set .Lasm_alt_mode, 0 148 .pushsection .altinstructions, "a" 149 altinstruction_entry 661f, \cb, ARM64_CB_PATCH, 662f-661f, 0 150 .popsection 151 661: 152 .endm 153 154 /* 155 * Provide the other half of the alternative code sequence. 156 */ 157 .macro alternative_else 158 662: 159 .if .Lasm_alt_mode==0 160 .subsection 1 161 .else 162 .previous 163 .endif 164 663: 165 .endm 166 167 /* 168 * Complete an alternative code sequence. 169 */ 170 .macro alternative_endif 171 664: 172 .if .Lasm_alt_mode==0 173 .previous 174 .endif 175 .org . - (664b-663b) + (662b-661b) 176 .org . - (662b-661b) + (664b-663b) 177 .endm 178 179 /* 180 * Callback-based alternative epilogue 181 */ 182 .macro alternative_cb_end 183 662: 184 .endm 185 186 /* 187 * Provides a trivial alternative or default sequence consisting solely 188 * of NOPs. The number of NOPs is chosen automatically to match the 189 * previous case. 190 */ 191 .macro alternative_else_nop_endif 192 alternative_else 193 nops (662b-661b) / AARCH64_INSN_SIZE 194 alternative_endif 195 .endm 196 197 #define _ALTERNATIVE_CFG(insn1, insn2, cap, cfg, ...) \ 198 alternative_insn insn1, insn2, cap, IS_ENABLED(cfg) 199 200 .macro user_alt, label, oldinstr, newinstr, cond 201 9999: alternative_insn "\oldinstr", "\newinstr", \cond 202 _asm_extable 9999b, \label 203 .endm 204 205 #endif /* __ASSEMBLY__ */ 206 207 /* 208 * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature)); 209 * 210 * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature, CONFIG_FOO)); 211 * N.B. If CONFIG_FOO is specified, but not selected, the whole block 212 * will be omitted, including oldinstr. 213 */ 214 #define ALTERNATIVE(oldinstr, newinstr, ...) \ 215 _ALTERNATIVE_CFG(oldinstr, newinstr, __VA_ARGS__, 1) 216 217 #endif /* __ASM_ALTERNATIVE_MACROS_H */ 218